Global emissions exceeding 'carbon budget', PwC study finds

World has emitted extra greenhouse gases this century equivalent to the annual totals of China and the United States, PricewaterhouseCoopers research finds

Guangan, China: A worker rides past coal-fuelled cooling towers at a power plant. The carbon 'debt' in 2008 was equivalent to the joint emissions of the US and China. Photograph: Frederic J Brown/AFP FREDERIC J. BROWN/AFP

The world is rapidly depleting its "carbon budget" for the first half of this century and must slash the carbon intensity of the global economy, a new report said today.

Economists and climate change experts at PricewaterhouseCoopers (PwC) said their new research highlights the need for an ambitious carbon reduction agreement at the Copenhagen climate conference, which starts next week.

The report's authors calculated the global carbon budget between 2000 and 2050 required to limit temperature rises to 2C, the climate threshold defined as "dangerous" by the EU.

A fifth of that budget had been used up by 2008, they said, meaning the world is already 10% off the necessary trajectory to hit the target. The carbon "debt" in 2008 was equivalent to the joint emissions of the US and China.

John Hawksworth, PwC's head of macroeconomics, said: "Despite the widening consensus around the need to decarbonise, few countries are doing enough to live within our estimates of their carbon budgets. "If the world stays on this [course] we will have used up the entire global carbon budget for the first half of this century by 2034, 16 years ahead of schedule."

The report added that the G20 countries which account for over 80% of global emissions need to cut their carbon intensity - the amount of carbon dioxide emitted for each unit of GDP - by 35% by 2020, four times the rate achieved between 2000 and 2008.

Global emissions from the use of energy need to peak by 2015 and fall back to 2009 levels by the end of the next decade, the report said.

Leo Johnson, a PwC climate change partner, said previous inaction meant that much faster action was needed now: "If we had started on a low-carbon pathway in 2000, we would have needed to decarbonise at around 2% a year up to 2008. We managed only 0.8% in 2000-08. The result is we now need to decarbonise at a rate of 3.5% a year to get back on track by 2020 - four times more than we have managed at the global level since 2000."

The report said that Britain, one of the first countries to set a legally binding carbon budget, has recorded the eighth best performance in the G20 in the period. The UK is behind France and Germany but ahead of Italy, and around 6-7% off the required trajectory to meet its carbon budget by 2050.

The EU as a whole, which claims leadership on the climate change agenda, is estimated to have been around 7% off target in 2008, having improved carbon intensity by 1.8% a year since 2000 compared to the 2.6% annually that would have been necessary to be on target.

Only Russia reduced its carbon intensity by more than the budgeted amount since 2000, thanks to very rapid increases in energy efficiency, although it started from a very low base.